Possible tendon issue?

We have just hatched some black jersery giants last week and I have one that wont stand up, I have tried to pull its legs straight to feel if the tendons have slipped but can only get it slightly past 90 degrees. It will hop around but I dont believe its using its feet as the toes are usally curled and somewhat limp. I have read about the treatment but am unsure as to how I can straighten its leg. Would simply streching it a little every day work? Any advice would be great! Thanks!